Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 2 2009 10.5194/hess-13-157-2009 http://www.hydrol-earth-syst-sci.net/13/157/2009/ http://www.hydrol-earth-syst-sci.net/13/157/2009/hess-13-157-2009.html http://www.hydrol-earth-syst-sci.net/13/157/2009/hess-13-157-2009.pdf 157 161 2009-02-18 <i>HESS Opinions</i> "The art of hydrology"* H. H. G. Savenije h.h.g.savenije@tudelft.nl Department of Water Management, Delft University of Technology, Delft, The Netherlands Unesco-IHE, Institute for Water Education, Delft, The Netherlands Invited contribution by H. H. G. Savenije, EGU Henry Darcy Medal award 2008. Hydrological modelling is the same as developing and encoding a hydrological theory. A hydrological model is not a tool but a hypothesis. The whole discussion about the inadequacy of hydrological models we have witnessed of late, is related to the wrong concept of what a model is. Good models don't exist. Instead of looking for the "best" model, we should aim at developing better models. The process of modelling should be top-down, learning from the data while at the same time connection should be established with underlying physical theory (bottom-up). As a result of heterogeneity occurring at all scales in hydrology, there always remains a need for calibration of models. This implies that we need tailor-made and site-specific models. Only flexible models are fit for this modelling process, as opposed to most of the established software or "one-size-fits-all" models. The process of modelling requires imagination, inspiration, creativity, ingenuity, experience and skill. These are qualities that belong to the field of art. Hydrology is an art as much as it is science and engineering. Beven, K. J.: Prophesy, reality and uncertainty in distributed hydrological modelling, Adv. Water Resour., 16, 41–51, 1993 Beven, K.: Towards integrated environmental models of everywhere: uncertainty, data and modelling as a learning process, Hydrol. Earth Syst. Sci., 11, 460–467, 2007. Fenicia, F., Savenije, H. H. G., and Avdeeva, Y.: Anomaly in the rainfall-runoff behaviour of the Meuse catchment. Climate, land use, or land use management?, Hydrol. Earth Syst. Sci. Discuss., 5, 1787–1819, 2008. Fenicia, F., Savenije, H H G., Matgen, P., and Pfister, L.: Understanding catchment behavior through stepwise model concept improvement, Water Resour. Res., 44, W01402, 1–13, doi:10.1029/2006WR005563, 2008b. Gumbricht, T., McCarthy, J., and McCarthy, T S.: Channels, wetlands and islands in the Okavango Delta, Botswana, and their relation to hydrological and sedimentological processes, Earth Surf. Proc. Land., 29(1), 15–29, 2004. Gumbricht, T., McCarthy, T S., and Bauer, P.: The micro-topography of the wetlands of the Okavango Delta, Botswana, Earth Surf. Proc. Land., 30(1), 27–39, 2005. Kinzelbach, W.: Hydrological Science and Engineering: the Yin and Yang of Water Resources Management, Geophysical Research Abstracts, Vol 10, EGU2008-A-10943, 2008. Savenije, H H G.: Equifinality, a blessing in disguise?, Hydrol. Process., 15, 2835–2838, 2001. Sivapalan, M., Blöschl, G., Zhang, L., and Vertessy, R.: Downward approach to hydrological prediction, Hydrol. Process., 17(11), 2101–2111, 2003. Wolski, P., Savenije, H H G., Murray-Hudson, M., and Gumbricht, T.: Modelling of the flooding in the Okavango Delta, Botswana, using a hybrid reservoir-GIS model, J. Hydrol., 331, 58–72, 2006.